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Introduction ⬇

Aldosterone is a mineralocorticoid hormone produced in the adrenal zona glomerulosa under complex control by the renin–angiotensin system. Its action is on the renal distal tubule, where it increases resorption of sodium and water at the expense of increased potassium excretion.

This test is useful in detecting primary or secondary aldosteronism (also called hyperaldosteronism). Patients with primary aldosteronism characteristically have hypertension, muscular pains and cramps, weakness, tetany, paralysis, and polyuria. This test is also used to evaluate causes of hypertension or low blood potassium levels and to check for adrenal tumors.

Normal Findings ⬆ ⬇

In Upright Position:

  • Adults: 7–30 ng/dL or 194–832 pmol/L

  • Adolescents: 4–48 ng/dL or 55–1331 pmol/L

  • Children: 5–80 mg/dL or 139–2220 pmol/L

In Supine Position:

  • Adults: 3–16 ng/dL or 83–444 pmol/L

  • Adolescents: 2–22 ng/dL or 55–610 pmol/L

  • Children: 3–35 mg/dL or 83–971 pmol/L

  • Low-sodium diet: values 3–5 times higher

Procedure ⬆ ⬇

  1. Obtain a 5-mL venous blood specimen in a heparinized or EDTA Vacutainer tube. Serum, EDTA, or heparinized blood may be used. The cells must be separated from plasma immediately. Blood should be drawn with the patient sitting, if possible. Observe standard precautions. Label the specimen with the patient’s name, date and time of collection, and test(s) ordered.

  2. Specify patient position (upright or supine) and record the site and time of the venipuncture. Circadian rhythm exists in normal subjects, with levels of aldosterone peaking in the morning, so it is best to obtain sample before 10 a.m. Specify if the blood has been drawn from the adrenal vein (values are much higher: 200–800 ng/dL or 5.5–22.6 nmol/L).

  3. A 24-hour urine specimen with boric acid preservative may also be ordered. Refrigerate immediately following collection.

  4. Have the patient follow a normal sodium diet 2–4 weeks before the test.

Clinical Implications ⬆ ⬇

  1. Elevated levels of aldosterone (primary aldosteronism) occur in the following conditions:

    1. Aldosterone-producing adenoma (Conn disease)

    2. Adrenocortical hyperplasia (pseudoprimary aldosteronism)

    3. Indeterminate hyperaldosteronism

    4. Glucocorticoid remediable hyperaldosteronism

  2. Secondary aldosteronism, in which aldosterone output is elevated because of external stimuli or greater activity in the renin–angiotensin system, occurs in the following conditions:

    1. Renovascular hypertension

    2. Salt depletion

    3. Potassium loading

    4. Laxative abuse

    5. Cardiac failure

    6. Cirrhosis of liver with ascites

    7. Nephrotic syndrome

    8. Bartter syndrome

    9. Diuretic abuse

    10. Hypovolemia and hemorrhage

    11. After 10 days of starvation

    12. Toxemia of pregnancy

  3. Decreased aldosterone levels are found in the following conditions:

    1. Aldosterone deficiency

    2. Primary adrenal insufficiency (e.g., Addison disease). Aldosterone is usually not affected in secondary adrenal insufficiency (hypopituitarism with decreased pituitary ACTH production) because the renin–angiotensin system is still intact

    3. Syndrome of renin deficiency (very rare)

    4. Low aldosterone levels associated with hypertension are found in Turner syndrome, diabetes, and alcohol intoxication

Interventions ⬆ ⬇

Pretest Patient Care

  1. Explain test purpose and procedures. Assess for history of diuretic or laxative abuse. If 24-hour urine specimen is required, follow protocols in Chapter 3.

  2. Discontinue diuretic agents, progestational agents, estrogens, and black licorice for 2 hours before the test.

  3. Ensure that the patient’s diet for 2 weeks before the test is normal (other than the previously listed restrictions) and includes 3 g/d (135 mEq/L/d) of sodium. Check with your laboratory for special protocols.

  4. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

Posttest Patient Care

  1. Have the patient resume normal activities and diet.

  2. Review test results and monitor appropriately for aldosteronism and aldosterone deficiency. Report and record findings. Modify the nursing care plan as needed.

  3. Follow guidelines in Chapter 1 for safe, effective, informed posttest care.

Interfering Factors ⬆

  1. Values are increased by upright posture.

  2. Recently administered radioactive medications affect test outcomes.

  3. Heparin therapy causes levels to fall. see Appendix E for drugs that increase or decrease levels.

  4. Thermal stress, late pregnancy, and starvation cause levels to rise.

  5. Aldosterone levels decrease with age.

  6. Many drugs—diuretic agents, antihypertensive drugs (such as spironolactone), progestogens, 
estrogens—and licorice should be terminated 2–4 hours before test.

Clinical Alert

  1. The simultaneous measurement of aldosterone and renin is helpful in differentiating primary from secondary hyperaldosteronism. Renin levels are high in secondary aldosteronism and low in primary aldosteronism.

  2. Potassium deficiencies should be corrected before testing for aldosterone.